WASHINGTON — Is the terrorist cold-bloodedly rational or utterly crazy? Has he chosen terror because it is his only method to achieve his goal--the "weapon of the weak"--or because it justifies a deep psychological need to commit violence?

These are not merely academic questions. As the potential grows for terrorists to have access to weapons of mass destruction, the answers increasingly matter.

According to the traditional view, expressed at a Smithsonian Institution conference here last week by Wesleyan University political scientist Martha Crenshaw, terrorism is a "political strategy," with resort to violence "a willful choice . . . rather than an unintended outcome."

Seek to Gain Attention

"Terrorism is theater," other experts have said, which seeks to get "lots of people watching, not lots of people killed." This view, comfortingly, seems to rule out one of the world's great nightmares--terrorism with nuclear weapons or poisonous chemicals.

Now, however, a growing body of experts contend that many terrorists have a psychological need to engage in violence. Far from using murder and destruction to achieve political ends, they intentionally avoid reaching their stated goals for fear of losing their excuse for violence.

"Political violence . . . (is) the end itself, not for all but for many," said George Washington University psychiatrist Jerrold M. Post. "The cause is not the cause. The cause, as codified in the group's ideology," he said, "becomes the rationale for acts the terrorists are driven to commit."

And the group mentality of terrorists, Post told the terrorism conference, leads to riskier choices than would have been made by individuals in the group.

"The internal constraints against the unthinkable prospect of nuclear terrorism are weakening," he warned. While still low, he said, "the prospects are increasing, and a major contribution to that increase are the risk-increasing group dynamics of the terrorist group."

Diversity of Groups

To a degree, the polar-opposite views of Crenshaw and Post may both be right. The Smithsonian's Walter Reich pointed out that "there are many different kinds of persons and groups who end up turning to what we call terrorism. We may call them 'they,' but if we attempt to predict future actions, we must disaggregate the 'they.' "

Some terrorists, he said, disdain nuclear and chemical terrorism. "But there are other groups with other needs, organized around other themes, for whom nuclear terrorism would be an acceptable activity. These groups tend to have more apocalyptic goals, more motivated by ideas, less concerned with establishing a state or homeland than an 'order' on earth."

One such group, native to the Western United States, is actually called The Order--a group allied with the racist Aryan Nations that has what Reich described as peculiar and potentially dangerous views about catastrophes as instruments of God's will. Reich said he does not believe that this group could carry out terrorism with nuclear weapons, but he noted that "a small quantity of highly radioactive material in the water supply could cause great harm, too."

Elsewhere in the world, he said, are other fringe religious groups that "seek to change the order of things, to cause the 'relocation of nature,' the establishment of God's will on Earth, for whom apocalypse is not only acceptable but could be necessary. Mass terrorism could fit into their realm."

Hezbollah's 'Sacred Mission'

Hezbollah, the "Party of God" in Lebanon, may be one. The Shia Muslim group and its adjuncts are blamed for suicide truck bombings of the U.S. Marine barracks and other foreign installations in Beirut as well as for kidnaping many of the Americans taken hostage in Lebanon. Hezbollah's "sacred mission" is to establish a pure Islamic state in Lebanon on the model of the Ayatollah Ruhollah Khomeini's regime in Iran.

Violence on the part of terrorist groups motivated by religious beliefs is on the rise, Reich said. He identified three other distinct types of terrorist groups:

--Ideological: West German, French and Italian terrorists of the 1960s and 1970s and the Weatherman faction of Students for a Democratic Society in the late 1960s and early 1970s in the United States. Violence by these groups, Reich said, seems to be declining.

--Nationalistic: the Palestine Liberation Organization and the Irish Republican Army.

--Separatist: the Basques of Spain, Sikhs of India and Tamils of Sri Lanka.

Post divides terrorists into the broader categories of "nationalist-separatists" and "anarchic-ideologues." The nationalists-separatists "are loyal to their parents, who are dissident to the regime," while the anarchists-ideologues are hostile to their families and, in their violence, are striking out at their parents who are identified with the Establishment.